Hummingbird vocalizations are usually displayed in two contexts. When foraging or defending territories, males and females usually display relative simple calls as territorial advertisement, while during courtship males perform individually elaborate songs to mate attraction or through singing assemblies (leks). About 15% of all described hummingbird species form leks or singing assemblies during the breeding season. However, the vocal repertoire displayed by males in these arenas has been rarely described. Here we studied the songs of Green Violetear Colibri thalassinus in a temperate forest from central Tlaxcala, Mexico, to document structure and variation within and between singing assemblies established over 3 years. We found 41 well differentiated and structurally complex syllable types across eleven recorded singing groups of Green Violetears (≈12 syllable types per singing group). The songs of most birds were repeats of the same 3–4 syllables, but the syllables types emitted can vary. Birds from the same lek tend to have similar song. Comparison of syllable sharing within-groups showed a Jaccard'similarity coefficient averaging 0.51 ± 0.09 (mean ± SD), and 0.24 ± 0.01 for among groups comparisons. These differences were corroborated by bootstrapping tests finding no significant similarity among males from different leks. However, significant similarity in syllable sharing was found between males from the same lek. No significant correlation was found between song similarity and geographic distances between leks. We have documented that static songs of lekking Green Violetears are more complex than had previously suggested. The variation of vocal repertoire among leks indicates the apparent presence of “vocal dialects” that are variable across time and space. The song variation in the context of discrimination ability in vocal neighborhoods requires further research.